Being overweight isn't a binary condition in these aircraft. They are certified within a specified envelope of CG and with for various kinds of operations. Going outside that envelope means that you are now a test pilot and you may discover singe very unusual and unpredictable behaviors. The plane may become uncontrollable under certain circumstances.

I once witnessed the set up to an accident of an aircraft that was overloaded. The pilot of the 172S proceeded to load four adults, full fuel, BBQ equipment's food into the little machine.

I had no idea about the BBQ or full fuel. I just saw for adults krilling around the plane as he preflighted it and thought that he must have planned carefully for a day like today. Apparently, he hadn't planned at all. It was 37C and fast and I had just returned from flying out to Montauk.

One of my tiedown ropes was damaged so I decided to replace it so it kept me heads down while my neighbor proceeded to load up and taxi away. When I finished and returned to my car, my wife told me that the group was going on a BBQ. When I asked how she knew that she said she watched them load out into the plane. I leapt out of the car to look for them, but it was too late.

The aircraft never made it off the ground being around 150 lbs over max gross. It crashed into the fence at the end of the airport near a busy highway. The fact that the aircraft was so badly overweight probably saved their lives. Thankfully that all came out uninjured but the aircraft was badly damaged.

Perhaps they may have just made it off the ground on a cold winter day with a low density altitude, maybe not. If they had, who know how long they would have been able to remain in the air. Maybe the first strong gust or the deployment of flaps would have caused an unrecoverable upset?

Flying GA airplanes sometimes significantly overweight has been relatively common, unfortunately. It is not a rare ingredient in the accidents either, if you look up some reports.

In principle, if your balance is ok, a moderately overweight airplane flies likely just fine, but performance lacks in comparison to specified. As the performance of a typical GA is nothing too spectacular to begin with, and the plane is probably flown as if it was within its W&B limits, problems are certainly expected.

That 2600 lbs is only about 2 % above what MTOW the airframe is certified (if using higher-rated power plant option). In that sense, there is really nothing much at all to note in the "physics" unless you look carefully. Obviously, the aircraft performance is lacking from the book values.

Flying GA airplanes sometimes significantly overweight has been relatively common, unfortunately. It is not a rare ingredient in the accidents either, if you look up some reports.

In principle, if your balance is ok, a moderately overweight airplane flies likely just fine, but performance lacks in comparison to specified. As the performance of a typical GA is nothing too spectacular to begin with, and the plane is probably flown as if it was within its W&B limits, problems are certainly expected.

That 2600 lbs is only about 2 % above what MTOW the airframe is certified (if using higher-rated power plant option). In that sense, there is really nothing much at all to note in the "physics" unless you look carefully. Obviously, the aircraft performance is lacking from the book values.

-Esa

Something I always stress to pilots when discussing over gross is that although true that an out of cg condition is the major player in the cg vs GW equation, taking off over gross is NOT something I recommend doing at ANY time.The reason for this caution is because an over gross condition changes every number on the stall speed starting with level flight and proceeding from there into the maneuvering envelope. An over gross aircraft flies at a higher angle of attack thus reducing the AOA spread the aircraft can use safely before reaching the wing's CLmax. Even more insidious and also associated is that the over gross condition also affects the airplane's Va.Pilots who fly over gross weight are indeed test pilots. There is danger all through the envelope for an aircraft being flown over gross.Dudley Henriques

Flying GA airplanes sometimes significantly overweight has been relatively common, unfortunately. It is not a rare ingredient in the accidents either, if you look up some reports.

In principle, if your balance is ok, a moderately overweight airplane flies likely just fine, but performance lacks in comparison to specified. As the performance of a typical GA is nothing too spectacular to begin with, and the plane is probably flown as if it was within its W&B limits, problems are certainly expected.

That 2600 lbs is only about 2 % above what MTOW the airframe is certified (if using higher-rated power plant option). In that sense, there is really nothing much at all to note in the "physics" unless you look carefully. Obviously, the aircraft performance is lacking from the book values.

-Esa

Something I always stress to pilots when discussing over gross is that although true that an out of cg condition is the major player in the cg vs GW equation, taking off over gross is NOT something I recommend doing at ANY time.The reason for this caution is because an over gross condition changes every number on the stall speed starting with level flight and proceeding from there into the maneuvering envelope. An over gross aircraft flies at a higher angle of attack thus reducing the AOA spread the aircraft can use safely before reaching the wing's CLmax. Even more insidious and also associated is that the over gross condition also affects the airplane's Va.Pilots who fly over gross weight are indeed test pilots. There is danger all through the envelope for an aircraft being flown over gross.Dudley Henriques

Yes absolutely. I seriously wouldn't mess with it.

A common airplane flown... "regularly" overweight is Cessna 150: two adults, and tanks full, and you tip the scale. I didn't know it back then but I have been on board one doing precisely that. Climb performance = nill; otherwise it flew fine. Steep turns and everything. Knowing better nowadays, I wouldn't go again if offered a ride without seeing the figures...152 perhaps!

Flying GA airplanes sometimes significantly overweight has been relatively common, unfortunately. It is not a rare ingredient in the accidents either, if you look up some reports.

In principle, if your balance is ok, a moderately overweight airplane flies likely just fine, but performance lacks in comparison to specified. As the performance of a typical GA is nothing too spectacular to begin with, and the plane is probably flown as if it was within its W&B limits, problems are certainly expected.

That 2600 lbs is only about 2 % above what MTOW the airframe is certified (if using higher-rated power plant option). In that sense, there is really nothing much at all to note in the "physics" unless you look carefully. Obviously, the aircraft performance is lacking from the book values.

-Esa

Something I always stress to pilots when discussing over gross is that although true that an out of cg condition is the major player in the cg vs GW equation, taking off over gross is NOT something I recommend doing at ANY time.The reason for this caution is because an over gross condition changes every number on the stall speed starting with level flight and proceeding from there into the maneuvering envelope. An over gross aircraft flies at a higher angle of attack thus reducing the AOA spread the aircraft can use safely before reaching the wing's CLmax. Even more insidious and also associated is that the over gross condition also affects the airplane's Va.Pilots who fly over gross weight are indeed test pilots. There is danger all through the envelope for an aircraft being flown over gross.Dudley Henriques

Yes absolutely. I seriously wouldn't mess with it.

A common airplane flown... "regularly" overweight is Cessna 150: two adults, and tanks full, and you tip the scale. I didn't know it back then but I have been on board one doing precisely that. Climb performance = nill; otherwise it flew fine. Steep turns and everything. Knowing better nowadays, I wouldn't go again if offered a ride without seeing the figures...152 perhaps!

-Esa

We used 150/152's in our student fleet. We kept at least one aircraft at 1/2 tanks (including our Aerobat) to accommodate any "over weight" students that happened to wander in for dual. LOLDH

We used 150/152's in our student fleet. We kept at least one aircraft at 1/2 tanks (including our Aerobat) to accommodate any "over weight" students that happened to wander in for dual. LOL

Leaving massive ~10 gallons of usable fuel in case of 150. It is not really an airplane to us who come in at about 200 lbs. Being 6 ft 2'' starts to be at the borderline of uncomfortable as well. Indeed, 152 is way better in this respect, carrying a whopping almost 600 lbs of total usable load. Oh my, these little things!

The ones I recall were mostly French-built Reims F150 series airplanes. I don't recall if there were any significant differences in specs. Even if the engine was Rolls-Royce...

But isn't 2% overweight wears down the engine and airframe faster? Plus what happens if I ran my engine at 112 psi oil pressure and I checked the maintenance hanger and nothing was wrong with the engine? I ran the engine with the defualt oil weight at -60F for two mins then reloaded it with warm weather and let the engine heat up to 125 degrees on the oil temp and pressure was at 112 or more don't remember it?

Not really. Airframe is regularly subjected to cyclic loads that are up to 100 % over the plane's own weight, and sometimes well beyond that even. Same goes with the engine, it depends on how you operate it and variables in normal operations make much bigger difference than a weight factor of few percent would. This is not where any important consequences would rise.

AbstractArtist wrote:

Plus what happens if I ran my engine at 112 psi oil pressure and I checked the maintenance hanger and nothing was wrong with the engine? I ran the engine with the defualt oil weight at -60F for two mins then reloaded it with warm weather and let the engine heat up to 125 degrees on the oil temp and pressure was at 112 or more don't remember it?

What was the default oil weight, I don't remember? That's a bit high but within limits. It should come down as your oil warms up. Constant operation at around or above maximum oil pressure basically increases chances for leaks and such.

Are you sure about that -60 °F? The engine would certainly be pre-heated to start in those conditions. Further, you'd certainly be using 20W-50 from the available oil options.

Not really. Airframe is regularly subjected to cyclic loads that are up to 100 % over the plane's own weight, and sometimes well beyond that even. Same goes with the engine, it depends on how you operate it and variables in normal operations make much bigger difference than a weight factor of few percent would. This is not where any important consequences would rise.

AbstractArtist wrote:

Plus what happens if I ran my engine at 112 psi oil pressure and I checked the maintenance hanger and nothing was wrong with the engine? I ran the engine with the defualt oil weight at -60F for two mins then reloaded it with warm weather and let the engine heat up to 125 degrees on the oil temp and pressure was at 112 or more don't remember it?

What was the default oil weight, I don't remember? That's a bit high but within limits. It should come down as your oil warms up. Constant operation at around or above maximum oil pressure basically increases chances for leaks and such.

Are you sure about that -60 °F? The engine would certainly be pre-heated to start in those conditions. Further, you'd certainly be using 20W-50 from the available oil options.

-Esa

I am using the default oil weight the one that's already in engine when plane is loaded the first time. What do you mean increase chance for oil leaks above 100 psi?

I am using the default oil weight the one that's already in engine when plane is loaded the first time. What do you mean increase chance for oil leaks above 100 psi?

Not above 100 psi or any other precise figure, but if a system containing fluid (oil, hydraulics, pneumatics...) is constantly operated above its designed pressure, it generally develops leaks faster. If I make up two systems with similar hoses, connections, seals etc. and run one at, say, 100 psi and another one at 300 psi, I'm fairly surely fixing the latter a lot more often. (Of course, high pressure systems therefore are not designed with similar hoses, connections and seals... ).

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